Conventionally, any sheet products made of paper, plastics, cloth, metal foil, etc. are first cut into a specific size by cutters, for example, by a sheet cutter or a guillotine cutter, and then defective sheets are eliminated by using a fault detector or by visual inspection of inspectors as required, and then a specific number of sheets are split into a single unit (hereinafter called "sheet stack"), which are finally packed and delivered.
When performing these operations, it is necessary to relocate sheet stacks in pile. It has long been practiced during the sheet cutting process to insert sheet marker papers into the cut sheets at specific intervals before operators manually grasp each sheet stack between the marker papers for delivery to ensuring processes. However, since each sheet stack contains a considerably heavy weight, operators have been not only obliged to sustain hard labor, but such a conventional practice also requires a considerably long time to carry out such serial operations. As a result, a variety of apparatuses capable of continuously delivering sheet stacks have gradually been developed in these years.
For example, an automatic paper feeder disclosed by the Japanese Utility Model Publication No. 21,704 of 1981 is designed to transfer a specific number of sheets in stack to the ensuing process after counting each piece of sheets from the sheet pile. Such an apparatus however contains a complex counting mechanism and costs a fairly long time for counting the actual number of sheets. On the other hand, an apparatus disclosed by the Japanese Patent Laid-Open No. 183,560 of 1983 uses a computer for converting the number of the required sheets into the layer thickness value before transferring the sheet layer thus defined. Such a device still needs to define the actual standard and grade of papers being dealt and the calculation needed for said conversion against each specific number of sheets, and in addition, it has an extremely complex mechanism for measuring the sheet layer thickness.
Another apparatus disclosed by the Japanese Patent Laid-Open No. 162,447 of 1983 provides such a mechanism designed for pushing forward an appropriate number of sheets from the sheet pile to ensuing processes by using a pusher unit. This device however cannot optionally provide a specific number of sheets for delivery because the number of sheets in stack is unavoidably constrained by the thickness of the sheet layer provided in conjunction with the pusher's capacity (normally, said thickness ranges from several centimeters to a maximum of 10 centimeters), i.e., it is unavoidably subject to the height for performing one-round lifting operation with a lift mounted with a sheet stack. The same also applies to such an apparatus which is provided with means for sandwiching sheet layers for transferring sheet stacks according to the disclosed Japanese Utility Model Publications of 1980, Nos. 36,421 and 47,779.
Likewise, there is a still further apparatus disclosed by the Japanese Utility Model Publication No. 13,738 of 1977, which is composed of such a mechanism designed for lifting the previously counted sheet stack from the level of a spacer inserted between sheet stacks. In this case, the spacer is designed to project itself from the edge line of the designated sheet stack along full width of the sheets, thus it unavoidably involves a complex handling operation, and yet, it may malfunction any time unexpectedly.
As a result, such conventional sheet stack delivery apparatuses not only contain such inherent disadvantages mentioned above, but also contain such additional disadvantages typically found in terms of slow operating speeds, and absence of such means for securely protecting full surface of the lifted sheets when being separated from the sheet pile, and thus, such conventional devices cannot effectively be applied to the delivery of delicate sheets such as art paper, coated paper and highglazed finish paper, etc.